[HEI451]

One thing to remember about MPG and vehicles of today is that those fuels are not as they were years ago, or, even 2, 3, 4 years ago. The main issue is the addition of Ethanol into the gasoline. Ethanol is grain alcohol, as E85 is. Depending on the percentage of Ethanol to gasoline, fuel mileage will get worse as the percentage of Ethanol goes up. It used to be that all grain enhanced fuels were 10 percent ethanol, and, mileage suffered to a percentage of that addition, but, just recently, the Ethanol percentage was upped by our lack luster government, from 10 to 15 percent, and that means fuel mileage goes down even more for it.

We must understand that alcohol fuels require richer fuel to air ratios, so, when we add Ethanol to gasoline, we effectively lean the fuel heat/light off burn-ability down, and that is like the older low octane fuels of the 1980's and 1990's, they required the throttle to be opened further to get the same power, and that meant more fuel usage for the amount of throttle opening. Add to this the leaner overall fuel to air mixtures built into the fuel systems of those vehicles, and mileage went south in one quick hurry.

Richening up the fuel curves for the Ethanol added fuels isn't the answer wither, all that does is make for more fuel usage. Very careful re-management of both injector duty cycles and creative ignition timing will help somewhat, but the return for the input doesn't bring the mileage all the way back. Very careful and sensible modifications to the fuel and ignition curves, modified exhaust systems and air inlet systems will help most of all, when all is done together, but individually, not much help. Also, "cooling off" engine operating temps only hurt mileage, as cooler inlet temps require more fuels, like a cold engine running on a carburetor needs a choke to operate when cold. Cooling off the engine temp cools the combustion chamber too much, and that demands richer mixtures, and loss of fuel mileage ensues.

Where I live in Northern Nevada, we just got 15 percent Ethanol doped up gasoline. We can tell the fuel mileages dropped considerably form that they were when we had only 10 percent Ethanol. My 1991 Buick park Avenue with 3.8 litre tuned port EFI V6 used to get 28 mpg on straight regular fuels, and when it went to 10 percent, mileage dropped to 21, and today, I filled up, calculated the mileage, with the new 15 percent, and it is now a whopping 16 mpg. I also daily ride a 1983 carburetted Honda GL650 V twin Silver Wing motorcycle that used to get 50 mpg with straight gas, with 10 percent, it dropped to 44 mpg, and now, with the 15 percent, down to 41/42 mpg.

Add to that the fuels are modified to make burn-ability "enhanced" for winter use and cold weather, vs summer fuels that have less volatility, and mileages are right dismal any more, even with the better EFI systems.

so, don't expect the mileage that is written on the window sticker, even if you drive with the proverbial "raw egg under your foot on the accelerator pedal", it just ain't gonna happen, because of government meddling and adverse additions to the fuels.